An embossing calender for thermoplastics material films generally of the above-described type is disclosed in German Auslegeschrift No. 1 436 891. In such calender, the film is embossed on one side by being passed through a roller gap between an embossing roller having a desired pattern on its external surface, and a counter-roller or auxiliary roller which has a resilient external surface. The film to be embossed is unwound from a roll or spool, embossed and then re-wound.
A film of thermoplastics material, such as polyvinyl chloride, is produced by a calender and is then drawn-out in a drawing device in a ratio of approximately two to one.
After the drawing process, the film passes into an embossing device which comprises an embossing roller, a resilient counter-roller and a drive roller. The counter-roller is provided with a resilient external surface of coating and is pressed against the drive roller by the embossing roller. This causes all of the rollers to be rotated simultaneously.
During the course of the embossing process, it is particularly important to ensure that the film is aligned at right angles to the longitudinal axis of the gap between the counter-roller and the embossing roller when it enters the gap. However, the film must not come into contact with either the embossing roller or the counter-roller before the embossing is effected.
If an extensive range of films are being produced on a single calendering system, it is highly desirable to be able to emboss, alternately, the underside or the top side of the film in dependence, of course, upon the type of film to be embossed.
Hitherto, when it was desired to change the side of a specific type of film to be embossed, complete dismantling of the embossing calender was necessary. This was mainly because the film had to be conducted either vertically or horizontally into the embossing gap without, however, having any prior contact with the rollers. Such a change-over procedure could well take an entire working day with the consequential loss of production.